ASM_MASM: Fix selection of ml64

Recognize 64-bit platforms based on the C or CXX architecture or
the platform specified with a VS generator name.

Modules/CMakeDetermineASM_MASMCompiler.cmake

@@ -17,7 +17,8 @@
 set(ASM_DIALECT "_MASM")
 
 # if we are using the 64bit cl compiler, assume we also want the 64bit assembler
-if(CMAKE_CL_64)
+if(";${CMAKE_VS_PLATFORM_NAME};${MSVC_C_ARCHITECTURE_ID};${MSVC_CXX_ARCHITECTURE_ID};"
+    MATCHES ";(Win64|Itanium|x64|IA64);")
    set(CMAKE_ASM${ASM_DIALECT}_COMPILER_INIT ml64)
 else()
    set(CMAKE_ASM${ASM_DIALECT}_COMPILER_INIT ml)